1. Field of the Invention
The present invention relates to an automatic suction and pressure valve having a valve seat, a valve stop and a sealing element that can move to and fro between the valve seat and the valve stop, and wherein at least one valve spring is arranged in a spring cup in the valve stop so as to load the sealing element against the valve seat.
2. The Prior Art
In suction and pressure valves, such as compressor valves, the sealing element is often loaded against the valve seat by valve springs, normally spiral springs, arranged in the valve stop. Such suction and pressure valves are known, for example from U.S. Pat. No. 1,593,914 A, which shows conical blind drilled holes to accommodate the spiral springs in the valve stop, and from EP 572 748 A1, which shows a cylindrical centering section at the bottom of a cylindrical blind drilled hole to accommodate the spiral springs. U.S. Pat. No. 3,536,094 A shows such a suction and pressure valve having individual rings as sealing elements.
In particular, the manufacture of spiral springs with a completely straight alignment and a ground section aligned completely normal to the axial direction of the spring is difficult, however. The majority of spiral springs have a slight angular deviation within predefined limits. Therefore, the compression of a spiral spring leads to a small force component normal to the deformation direction and, as a result, the angular deviation is further promoted. Angled spiral springs and/or force components normal to the axial direction of the spiral spring assist the rotation of the sealing element, for example of a valve plate or a number of valve rings in ring valves. In addition, a non-uniform inlet flow around the sealing element in valves generally leads to the non-parallel movement of the sealing element and, in the case of ring valves, to ring rotation. During the operation of the suction and pressure valve, all this leads to a deflection of the valve spring out of the axial direction. In particular in the case of ring valves, the ring rotation can cause severe deflection of the valve springs normal to the axial direction.
As a result of a deflection of the valve spring normal to the axial direction, contact occurs between the valve spring, which is usually fabricated from steel, and the (metallic) valve stop. The contact with the (metallic) valve stop leads to wear and damage to the spring and also to the valve stop itself and, as a result, to a reduced lifetime of valve spring and/or valve stop. For this reason, years ago spring cups began to be arranged in the valve stop in suction and pressure valves, in particular compressor valves, the valve springs being inserted and guided in said spring cups in order to avoid spring wear and wear on the valve stop.
Spring cups are also used in ring valves in order, for the purpose of adequate support and guidance of the springs even in the case of restricted installation conditions, to be able to use springs with a diameter which corresponds substantially to the width of a ring, as can be gathered for example from EP 1 247 982 A2.
However, it has been observed that, despite the use of spring cups, it is possible for wear problems with the springs to occur. The reason for this is that, in the case of highly impact-stressed valve springs, the first and last spring turns are stressed up to twice as highly as the spring turns in the central region, because of the reflection of the shock waves. In the event of more intense rotation of the sealing element or more intense deflection of the spring, however, in the case of conventional spring cups the spring touches the edge of the spring cup with the spring end which is most highly loaded. In this case, either damage occurs to the spring cup or, even more critically, wear occurs on the critical turns of the spring or a spring fracture occurs, caused by the hindrance to movement of the spring.
It is therefore an object of the present invention to eliminate the abovementioned disadvantages of conventional spring cups and, in particular, to reduce wear at the spring ends of the valve spring arranged in the spring cup to the greatest possible extent, in order to increase the lifetime in particular of the valve springs.